1. Field of the Invention
The present invention relates to a numerical control method and a system therefor in which it is possible to carry out numerical control automatically repeatedly in accordance with a numerical control program modified by utilization of an override function.
2. Description of the Related Art
There is a numerical control system (hereinafter referred to as "NC system") of a type which is provided with an override function for modifying, during operation of the NC system, control condition parameter values designated by an NC program (part program). Hitherto, for example, in a machine tool controlled by the NC system of this kind, the override function is utilized, during operation of the machine tool, to adjust a cutting feed speed and a spindle speed designated in an NC work program so as to increase and decrease these speeds in compliance with a workpiece working configuration, workpiece material and an actual working state. However, the conventional speed adjustment using the override function is performed by manual operation of override switches (override dials) provided on the NC system, and is effective only against working in course of being currently carried out. Accordingly, if an attempt is made to continue to carry out work under the previously modified working conditions, as far as the same NC work program is used, the override switches must again be manually operated in like manner at a point of time when the feed speed and the spindle speed have previously been modified, to modify these speeds.